Handle unreadable archives and adjust cron job configuration

- Skip page count assignment for corrupt or incompatible archives in comic processing.
- Update `Dockerfile` to append crontab entries to `/etc/crontab` instead of `/etc/cron.daily/cbreader`.
- Modify crontab entry to use the virtual environment's Python binary and include the `root` user for execution.

Dockerfile

@@ -31,6 +31,6 @@ RUN cd frontend \
     && rm -r node_modules
 
 
-RUN cat /src/cbreader/crontab >> /etc/cron.daily/cbreader
+RUN cat /src/cbreader/crontab >> /etc/crontab
 
 EXPOSE 8000